Heterojunction solar cell, method for manufacturing the same, and photovoltaic module

Abstract

The application relates to the field of solar cells, and discloses a heterojunction solar cell, a preparation method thereof and a photovoltaic module. The preparation method comprises the following steps: providing a substrate with a first passivation silicon layer, the first passivation silicon layer comprising a first surface facing away from the substrate and a second surface facing the substrate; performing a doping treatment on the first surface of the first passivation silicon layer by using a doping gas source and an auxiliary gas source; depositing a first doped silicon layer on the first surface; and post-treatment, so as to obtain the heterojunction solar cell. The auxiliary gas source is a first silane and / or an impurity source for forming the first doped silicon layer, and the doping gas source contains carbon elements and / or oxygen elements. The first doped silicon layer prepared by using the application has good light transmittance and can effectively improve the crystallization rate, thereby helping to improve the photoelectric conversion efficiency of the heterojunction solar cell to a higher degree.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a heterojunction solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] In the process of fabricating heterojunction solar cells, adding oxygen to the doped silicon layer can improve light transmittance, but it also leads to a lower crystallinity in the doped silicon layer. This makes the light transmittance and crystallinity of the doped silicon layer mutually restrictive, thus making it difficult to effectively improve the photoelectric conversion efficiency of heterojunction solar cells. Summary of the Invention

[0003] This application discloses a heterojunction solar cell, its fabrication method, and a photovoltaic module. The first doped silicon layer prepared using this application has both good light transmittance and effectively improves its crystallinity, thereby contributing to a significant increase in the photoelectric conversion efficiency of the heterojunction solar cell.

[0004] In the first aspect, this application discloses a method for fabricating a heterojunction solar cell, the method comprising the following steps: A substrate having a first passivated silicon layer is provided, the first passivated silicon layer including a first surface facing away from the substrate and a second surface facing the substrate; The first surface of the first passivated silicon layer is doped using a doping gas source and an auxiliary gas source. A first doped silicon layer is deposited on the first surface; Post-processing yields the heterojunction solar cell; The auxiliary gas source is a first silane and / or an impurity source used to form the first doped silicon layer, wherein the doped gas source contains carbon and / or oxygen elements.

[0005] Furthermore, the flow rate ratio of the auxiliary gas source to the doped gas source is 1:50 to 1:200.

[0006] Furthermore, the first surface is subjected to the doping treatment using PECVD, with an ignition time of 4 s to 10 s, an ignition power of 2000 W to 3000 W, and a pressure of 1 Torr to 1.5 Torr.

[0007] Furthermore, the doping gas source includes at least one of carbon dioxide, nitrous oxide, and methane; and / or, When the auxiliary gas source includes the impurity source, the impurity source satisfies one of the following conditions: When the first doped silicon layer is a P-type doped layer, the impurity source in the auxiliary gas source includes at least one of BH3, TMB, BCl3, and B2H6. When the first doped silicon layer is an N-type doped layer, the impurity source in the auxiliary gas source includes PH3.

[0008] Furthermore, when the first doped silicon layer is prepared using the PECVD method, the pressure is 6 Torr to 9 Torr.

[0009] Furthermore, when preparing the first doped silicon layer, the deposition gas source includes a second silane and a first hydrogen gas, the flow ratio of the second silane and the first hydrogen gas is 1:50 to 1:200, and the ignition power is 15000 W to 20000 W.

[0010] Furthermore, after the step of depositing the first doped silicon layer on the first surface and before the post-processing step, the fabrication method further includes: fabricating a second doped silicon layer on the first doped silicon layer; When the second doped silicon layer is prepared by PECVD, the deposition gas source includes a third silane, the impurity source and a second hydrogen gas. The flow rate ratio of the third silane, the impurity source and the second hydrogen gas is 1:(0.2~2.5):(200~400), the ignition power is 30000 W~50000 W, and the pressure is 4.5 Torr~5.8 Torr.

[0011] Furthermore, before the step of doping the first surface of the first passivated silicon layer with an auxiliary gas source and a doping gas source, the preparation method further includes: sequentially preparing a second passivated silicon layer, a third passivated silicon layer, a fourth passivated silicon layer, and the first passivated silicon layer on a substrate; In the process of preparing the second passivated silicon layer using PECVD, the deposition gas source includes a fourth silane, wherein the flow rate of the fourth silane is 3000 sccm~5000 sccm, the ignition power is 2000 W~3000 W, and the pressure is 0.5 Torr~10.8 Torr; and / or, When preparing the third passivated silicon layer using PECVD, the deposition gas source includes a fifth silane, wherein the flow rate of the fifth silane is 3000 sccm~5000 sccm, the ignition power is 2000 W~3000 W, and the pressure is 0.3 Torr~0.5 Torr; and / or, When the fourth passivated silicon layer is prepared using PECVD, the deposition gas source includes a sixth silane and a third hydrogen gas, with a flow rate ratio of 1:0.5 to 1:2, an ignition power of 500 W to 1000 W, and a pressure of 0.3 Torr to 0.6 Torr; and / or, When the first passivated silicon layer is prepared by PECVD, the deposition gas source includes seventh silane and fourth hydrogen, the flow ratio of the seventh silane and the fourth hydrogen is 1:10 to 1:30, the ignition power is 10000 W to 20000 W, and the pressure is 1 Torr to 1.5 Torr.

[0012] Secondly, this application discloses a heterojunction solar cell, wherein the heterojunction solar cell comprises the heterojunction solar cell prepared by the preparation method described in any one of the first aspects.

[0013] Furthermore, the heterojunction solar cell includes a substrate, and a passivated silicon layer, a doped silicon layer, a transparent conductive layer, and an electrode sequentially stacked on the substrate; The passivation silicon layer includes a second passivation silicon layer, a third passivation silicon layer, a fourth passivation silicon layer, and a first passivation silicon layer stacked on the substrate; the doped silicon layer includes a first doped silicon layer and a second doped silicon layer stacked sequentially on the first passivation silicon layer.

[0014] Furthermore, the crystallinity of the doped silicon layer is 60%~80%; and / or, The light transmittance of the doped silicon layer is 70%~95%; and / or, The thickness of the second doped silicon layer is 20 nm to 30 nm; and / or, The thickness of the first doped silicon layer is 1.5 nm to 2 nm; and / or, The thickness of the first passivated silicon layer is 2.5 nm to 4 nm; and / or, The thickness of the second passivated silicon layer is 0.5 nm to 1.5 nm; and / or, The thickness of the third passivation silicon layer is 0.1 nm to 1 nm; and / or, The thickness of the fourth passivation silicon layer is 1.8 nm to 2.5 nm.

[0015] Thirdly, this application discloses a photovoltaic module, which includes: the heterojunction solar cell described in any one of the second aspects.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: In the fabrication of heterojunction solar cells, this application optimizes the structure of the first doped silicon layer by performing a doping treatment on the first surface of the first passivated silicon layer before fabricating the first doped silicon layer. This allows the first doped silicon layer to have both good light transmittance and effectively improve its crystallinity, thereby contributing to a higher degree of improvement in the photoelectric conversion efficiency of the heterojunction solar cell.

[0017] In this application, instead of directly preparing a first doped silicon layer on a substrate with a first passivated silicon layer, a doping gas source and an auxiliary gas source are used to dope the first surface of the first passivated silicon layer. By doping the first surface, the doped first surface can be used as a crystallization induction source for the first doped silicon layer. Therefore, in the subsequent preparation of the first doped silicon layer, there is no need to introduce an additional oxygen source as a crystallization induction source.

[0018] Specifically, during the doping process, carbon and / or oxygen elements in the doping gas source combine with silicon elements on the first surface to form Si-O bonds and / or Si-C bonds. When the first doped silicon layer is prepared, these chemical bonds can act as crystallization induction sources for the first doped silicon layer, providing abundant nucleation sites to promote the orderly arrangement of atoms in the first doped silicon layer, thereby forming a structurally ordered and highly crystalline first doped silicon layer. This further helps to improve the crystallinity of the first doped silicon layer and enhance its light transmittance.

[0019] Furthermore, the use of a doping gas source generates dangling bonds on the surface of the first passivated silicon layer. When the auxiliary gas source includes a first silane, the first silane decomposes to form free radicals (SiH3· and / or SiH2·) and hydrogen atoms. Thus, the free radicals and / or hydrogen atoms passivate the dangling bonds, thereby ensuring the performance of the first passivated silicon layer to a high degree. When the auxiliary gas source includes an impurity source, the first surface of the first passivated silicon layer will have doping elements from the impurity source. The presence of doping elements changes the energy band of the first surface, making the interface barrier between the first doped silicon layer and the first surface smaller, reducing the recombination loss of charge carriers at the interface, thereby improving the photoelectric conversion efficiency of the solar cell to a high degree. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a process flow diagram of a heterojunction solar cell provided in an embodiment of this application; Figure 2 This is a process flow diagram of another heterojunction solar cell provided in the embodiments of this application; Figure 3 This is a schematic diagram of a solar cell structure provided in an embodiment of this application (showing the specific film structure of the passivation silicon layer). Figure 4This is a schematic diagram of the structure of a solar cell provided in an embodiment of this application (showing the specific film structure of the doped silicon layer).

[0022] Icons: 1. Substrate; 11. Light-receiving surface; 12. Backlight-receiving surface; 2. Passivation silicon layer; 21. First passivation silicon layer; 22. Second passivation silicon layer; 23. Third passivation silicon layer; 24. Fourth passivation silicon layer; 3. Doped silicon layer; 31. First doped silicon layer; 32. Second doped silicon layer; 4. Transparent conductive layer; 5. Electrode. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0025] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0026] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0027] The technical solutions provided in this application will be further described below with reference to the embodiments and accompanying drawings.

[0028] In the doped silicon layer of heterojunction solar cells, the doped silicon layer needs to simultaneously possess high crystallinity and high light transmittance. However, these two properties have opposite requirements for oxygen content, making it difficult to achieve both at the same time.

[0029] Specifically, the surface of the passivated silicon layer contains numerous silicon dangling bonds, which hinder the orderly arrangement of silicon atoms in the doped silicon layer. When trace amounts of oxygen are introduced, oxygen can form silicon-oxygen bonds with the silicon dangling bonds, effectively reducing density defects and thus promoting crystal nucleation. At the same time, the high electronegativity of oxygen induces the surrounding silicon atoms to rearrange, thereby increasing the crystallinity of the doped silicon layer.

[0030] However, when the oxygen content is too high, although the high oxygen content can widen the band gap of the doped silicon layer and help improve the light transmittance, the high oxygen content will cause some oxygen atoms to combine with silicon atoms inside the doped silicon layer to form a large number of silicon-oxygen bonds. The presence of these bonds will destroy the mobility of silicon atoms inside the doped silicon layer, inhibit the orderly arrangement of silicon atoms, and lead to a decrease in the crystallinity of the doped silicon layer.

[0031] Therefore, a low oxygen content is beneficial for crystallization but insufficient to optimize light transmittance; while a high oxygen content can improve light transmittance, it comes at the cost of sacrificing crystallization rate. The two requirements for oxygen content are conflicting and cannot be achieved simultaneously.

[0032] Based on the above problems, this application provides a heterojunction solar cell and its preparation method, as well as a photovoltaic module. The doped silicon layer prepared by the preparation method of this application has both high crystallinity and good light transmittance.

[0033] This application discloses a method for fabricating a heterojunction solar cell, such as... Figure 1 As shown, the preparation method includes the following steps: A substrate having a first passivated silicon layer is provided, the first passivated silicon layer including a first surface facing away from the substrate and a second surface facing the substrate; The first surface of the first passivated silicon layer is doped using a doping gas source and an auxiliary gas source. A first doped silicon layer is deposited on the first surface; Post-processing yields heterojunction solar cells; The auxiliary gas source is a first silane and / or an impurity source used to form the first doped silicon layer, and the doped gas source contains carbon and / or oxygen elements.

[0034] In this application, instead of directly fabricating a first doped silicon layer on a substrate with a first passivated silicon layer already formed, a doping gas source and an auxiliary gas source are used to dope the first surface of the first passivated silicon layer. By doping the first surface, the doped first surface can serve as a crystallization induction source to induce the first doped silicon layer to crystallize. Therefore, in the subsequent fabrication of the first doped silicon layer, there is no need to introduce an additional oxygen source as a crystallization induction source.

[0035] Specifically, during the doping process, carbon and / or oxygen elements in the doping gas source combine with silicon elements on the first surface to form Si-O bonds and / or Si-C bonds. When preparing the first doped silicon layer, these chemical bonds can act as crystallization induction sources, providing abundant nucleation sites to promote the orderly arrangement of atoms in the first doped silicon layer, thereby forming a structurally ordered and highly crystalline first doped silicon layer and improving its crystallinity. A higher crystallinity indicates a lower defect state density in the first doped silicon layer, which further helps to reduce parasitic absorption and improve the solar energy utilization rate of the first doped silicon layer.

[0036] Furthermore, the use of a doping gas source generates dangling bonds on the surface of the first passivated silicon layer. When the auxiliary gas source includes a first silane, the first silane decomposes to form free radicals (SiH3· and / or SiH2·) and hydrogen atoms. Thus, the free radicals and / or hydrogen atoms passivate the dangling bonds, thereby optimizing the passivation performance of the first passivated silicon layer to a high degree. When the auxiliary gas source includes an impurity source, the first surface of the first passivated silicon layer will have doping elements from the impurity source. The presence of doping elements changes the energy band of the first surface, making the interface barrier between the first doped silicon layer and the first surface smaller, reducing the recombination loss of charge carriers at the interface, thereby improving the photoelectric conversion efficiency of the solar cell to a high degree.

[0037] In summary, before preparing the first doped silicon layer, this application first performs doping treatment on the first surface of the first passivated silicon layer, thereby enabling the first doped silicon layer to have good light transmittance, effectively improve its crystallinity, and effectively reduce the interfacial barrier between the charge carriers and the first doped silicon layer, which in turn helps to improve the photoelectric conversion efficiency of the heterojunction solar cell to a greater extent.

[0038] Here, the impurity source refers to a gas source that imparts an N-type or P-type conductivity to the first doped silicon layer. Specifically, when the first doped silicon layer is a P-type doped layer, the impurity source in the auxiliary gas source includes at least one of BH3, TMB, BCl3, and B2H6; or, when the first doped silicon layer is an N-type doped layer, the impurity source in the auxiliary gas source includes PH3.

[0039] The doping gas source includes at least one of carbon dioxide, nitrous oxide, and methane. More preferably, when the doping gas source is carbon dioxide, there are both silicon-carbon bonds and silicon-oxygen bonds at the interface, which helps to improve the crystallinity of the first doped silicon layer. In addition, oxygen can passivate the dangling bonds on the first surface and reduce the recombination loss of charge carriers, thereby helping to improve the photoelectric conversion efficiency of the solar cell to a greater extent.

[0040] Furthermore, the preparation method provided in this application can be applied to the preparation process of the doped silicon layer on the light-receiving side of the substrate or the preparation process of the doped silicon layer on the backlight side, or it can be applied to both the preparation process of the doped silicon layer on the light-receiving side of the substrate and the preparation process of the doped silicon layer on the backlight side.

[0041] Furthermore, the flow rate ratio of the auxiliary gas source to the doping gas source is 1:50 to 1:200. During the introduction of the doping gas source, a small amount of dangling bonds or defects are introduced. Simultaneously, the introduced first silane decomposes to form free radicals (SiH3 / SiH2) and hydrogen atoms. These hydrogen atoms and free radicals can fill defects, saturate dangling bonds, and reduce carrier recombination losses. This application further controls the flow rate ratio within the above range, resulting in a higher match between the content of free radicals and hydrogen atoms formed by the decomposition of the introduced first silane and the content of dangling bonds introduced by the doping gas source, thereby effectively improving the passivation effect of the first passivation silicon layer. In addition, it also ensures an appropriate content of silicon-oxygen and / or silicon-carbon bonds at the first surface, thereby effectively inducing the crystallization of the first doped silicon layer and improving its crystallinity. For example, the flow rate ratio is 1:50, 1:80, 1:110, 1:140, 1:170, or 1:200, etc.

[0042] When the doped gas source contains oxygen, it is easier to introduce dangling bonds or defects. Therefore, controlling the flow ratio of the auxiliary gas source and the doped gas source within the above range helps to further ensure the passivation effect of the first passivation silicon layer and improve the photoelectric conversion efficiency of the heterojunction solar cell.

[0043] Furthermore, the first surface is doped using PECVD, with an ignition time of 4 to 10 s, an ignition power of 2000 W to 3000 W, and a pressure of 1 to 1.5 Torr. By controlling the preparation parameters within the above range, the doping effect on the first surface can be effectively ensured, promoting the decomposition of the first silane and resulting in abundant Si-C and / or Si-O bonds at the first surface of the first passivated silicon layer. This also helps to reduce the adverse effects on the first passivated silicon layer. For example, the ignition time is 4 s, 5.5 s, 7 s, 8.5 s, or 10 s, etc.; the ignition power is 2000 W, 2200 W, 2400 W, 2600 W, 2800 W, or 3000 W, etc.; and the pressure is 1 Torr, 1.2 Torr, 1.3 Torr, 1.4 Torr, or 1.5 Torr, etc.

[0044] Furthermore, when preparing the first doped silicon layer using PECVD, the pressure is 6 Torr to 9 Torr. The applicant has found that the first surface, after treatment with the auxiliary gas source and doping gas source, exhibits higher film sensitivity and lower density, making the first doped silicon layer more susceptible to damage. Therefore, this application increases the deposition pressure from the conventional 4 Torr to 6 Torr to 9 Torr during the preparation of the first doped silicon layer. This increased deposition pressure lowers ion energy, resulting in weaker bombardment force when ions reach the first surface. This helps to significantly reduce the damage to the first passivation silicon layer, thereby significantly improving the photoelectric conversion efficiency of the heterojunction solar cell. Examples of pressures include 6 Torr, 6.8 Torr, 7 Torr, 7.3 Torr, 8.2 Torr, or 9 Torr.

[0045] Furthermore, during the preparation of the first doped silicon layer, the deposition gas source includes a second silane and a first hydrogen gas, with a flow rate ratio of 1:50 to 1:200 and an ignition power of 15000 W to 20000 W. This application does not use an oxygen-containing source during the preparation of the first doped silicon layer, thereby effectively improving the film density of the first doped silicon layer and helping to suppress hydrogen diffusion into the first passivation silicon layer, thus significantly improving the film integrity of the first passivation silicon layer. In addition, oxygen, as an amorphization promoter, also helps reduce its negative impact on the crystallinity of the first doped silicon layer by not using an oxygen-containing source, thus significantly improving the crystallinity of the first doped silicon layer. Furthermore, it effectively avoids the adverse effects of using an oxygen-containing source on the activation of impurity sources, further contributing to improved performance of the first doped silicon layer. For example, the flow ratio is 1:50, 1:80, 1:110, 1:150 or 1:200, etc.; the ignition power is 15000 W, 16000 W, 17000 W, 18000 W or 20000 W, etc.

[0046] Furthermore, such as Figure 2 As shown, after the step of depositing the first doped silicon layer on the first surface and before the post-processing step, the fabrication method further includes: fabricating a second doped silicon layer on the first doped silicon layer; In the preparation of the second doped silicon layer using PECVD, the deposition gas source includes a third silane, an impurity source, and a second hydrogen gas. The flow rate ratio of the third silane, the impurity source, and the second hydrogen gas is 1:(0.2~2.5):(200~400), the ignition power is 30000 W~50000 W, and the pressure is 4.5 Torr~5.8 Torr. This application does not use an oxygen-containing source when preparing the second doped silicon layer, which effectively improves the film density of the second doped silicon layer and helps suppress hydrogen diffusion into the first passivation silicon layer, thereby ensuring the integrity of the first passivation silicon layer to a high degree. Furthermore, since oxygen acts as an amorphization promoter, the absence of an oxygen-containing source in the preparation of the second doped silicon layer also helps reduce its negative impact on the crystallinity of the second doped silicon layer, thus significantly improving the crystallinity. In addition, it effectively avoids the adverse effects of using an oxygen-containing source on impurity source activation, further contributing to improved performance of the second doped silicon layer. For example, the flow ratio is 1:0.2:200, 1:1:250, 1:1.5:300, 1:2:350 or 1:2.5:400, etc.; the ignition power is 30000 W, 35000 W, 40000 W, 45000 W or 50000 W, etc.; the pressure is 4.5 Torr, 4.7 Torr, 4.9 Torr, 5.1 Torr, 5.5 Torr or 5.8 Torr, etc.

[0047] Furthermore, before the step of doping the first surface of the first passivated silicon layer with an auxiliary gas source and a doping gas source, the preparation method further includes: sequentially preparing a second passivated silicon layer, a third passivated silicon layer, a fourth passivated silicon layer, and a first passivated silicon layer on a substrate; In the PECVD method for preparing the second passivated silicon layer, the deposition gas source includes a fourth silane, with a flow rate of 3000 sccm to 5000 sccm, an ignition power of 2000 W to 3000 W, and a pressure of 0.5 Torr to 10.8 Torr. By controlling the parameters for preparing the second passivated silicon layer within the above range, the quality of the prepared second passivated silicon layer can be effectively ensured, thereby contributing to a significant improvement in the anti-epitaxial effect of the second passivated silicon layer. For example, the flow rate can be 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, or 5000 sccm; the ignition power can be 2000 W, 2200 W, 2400 W, 2600 W, or 3000 W; and the pressure can be 0.5 Torr, 2 Torr, 4 Torr, 6 Torr, 8 Torr, or 10.8 Torr.

[0048] When preparing the third passivated silicon layer using PECVD, the deposition gas source includes silane 5, with a flow rate of 3000 sccm to 5000 sccm, an ignition power of 2000 W to 3000 W, and a pressure of 0.3 Torr to 0.5 Torr. By controlling the parameters for preparing the third passivated silicon layer within the above range, the quality of the prepared third passivated silicon layer can be effectively ensured, thereby contributing to a significant improvement in the anti-yellowing effect of the third passivated silicon layer. For example, the flow rate can be 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, or 5000 sccm; the ignition power can be 2000 W, 2200 W, 2400 W, 2600 W, or 3000 W; and the pressure can be 0.3 Torr, 0.35 Torr, 0.4 Torr, 0.45 Torr, or 0.5 Torr.

[0049] When preparing the fourth passivation silicon layer using PECVD, the deposition gas source includes sixth silane and third hydrogen, with a flow rate ratio of 1:0.5 to 1:2, an ignition power of 500 W to 1000 W, and a pressure of 0.3 Torr to 0.6 Torr. By controlling the parameters for preparing the fourth passivation silicon layer within the above range, the quality of the prepared fourth passivation silicon layer can be effectively ensured, thereby contributing to a significant improvement in the passivation effect. Examples include flow rates of 1:0.5, 1:0.9, 1:1.2, 1:1.6, or 1:2; ignition powers of 500 W, 650 W, 800 W, 900 W, or 1000 W; and pressures of 0.3 Torr, 0.37 Torr, 0.42 Torr, 0.5 Torr, or 0.6 Torr.

[0050] When preparing the first passivated silicon layer using PECVD, the deposition gas source includes septane and hydrogen, with a flow rate ratio of septane to hydrogen of 1:10 to 1:30, an ignition power of 10,000 W to 20,000 W, and a pressure of 1 Torr to 1.5 Torr. By controlling the parameters for preparing the first passivated silicon layer within the above range, the quality of the prepared first passivated silicon layer can be effectively ensured, thereby contributing to a significant improvement in the passivation effect. Examples include flow rates of 1:10, 1:15, 1:20, 1:25, or 1:30; ignition powers of 10,000 W, 12,000 W, 14,000 W, 16,000 W, or 20,000 W; and pressures of 1 Torr, 1.1 Torr, 1.2 Torr, 1.3 Torr, or 1.5 Torr.

[0051] This application provides an embodiment of a heterojunction solar cell, which includes the heterojunction solar cell prepared by the above-described preparation method.

[0052] Furthermore, such as Figure 3 and Figure 4 As shown, the heterojunction solar cell includes a substrate 1, which includes a light-receiving surface 11 and a back-lighting surface 12 disposed opposite to each other. A passivation silicon layer 2, a doped silicon layer 3, a transparent conductive layer 4 and an electrode 5 are sequentially stacked on the light-receiving surface 11. A passivation silicon layer 2, a doped silicon layer 3, a transparent conductive layer 4 and an electrode 5 are sequentially stacked on the back-lighting surface 12. The passivation silicon layer 2 includes a second passivation silicon layer 22, a third passivation silicon layer 23, a fourth passivation silicon layer 24 and a first passivation silicon layer 21 stacked on the substrate 1; the doped silicon layer 3 includes a first doped silicon layer 31 and a second doped silicon layer 32 stacked sequentially on the first passivation silicon layer 21.

[0053] Furthermore, the crystallinity of the doped silicon layer 3 is 60% to 80%. The crystallinity of the doped silicon layer 3 prepared using the method of this application is increased from 40% to 55% to 60% to 80%, which further helps to ensure the conductivity of the doped silicon layer 3 and improve its light transmittance. Exemplarily, the crystallinity is 60%, 65%, 70%, 75%, or 80%, etc.

[0054] Furthermore, the light transmittance of the doped silicon layer 3 is 70% to 95%. When the crystallinity of the doped silicon layer 3 is within the above range, it indicates a high degree of absorption and utilization of sunlight, which further helps to improve the photoelectric conversion efficiency of the heterojunction solar cell. For example, the light transmittance is 70%, 76%, 81%, 88%, or 95%, etc.

[0055] Furthermore, the thickness of the second doped silicon layer 32 is 20 nm to 30 nm; the thickness of the first doped silicon layer 31 is 1.5 nm to 2 nm. By setting the thicknesses of the second doped silicon layer 32 and the first doped silicon layer 31 within the above ranges, they exhibit a high degree of synergy, thereby contributing to a significant improvement in the performance of the doped silicon layer 3. For example, the thickness of the second doped silicon layer 32 is 20 nm, 22 nm, 24 nm, 26 nm, or 30 nm, etc.; the thickness of the first doped silicon layer 31 is 1.5 nm, 1.6 nm, 1.7 nm, 1.9 nm, or 2 nm, etc.

[0056] Furthermore, the thickness of the first passivation silicon layer 21 is 2.5 nm to 4 nm; the thickness of the second passivation silicon layer 22 is 0.5 nm to 1.5 nm; the thickness of the third passivation silicon layer 23 is 0.1 nm to 1 nm; and the thickness of the fourth passivation silicon layer 24 is 1.8 nm to 2.5 nm. By controlling the thickness of the film layers within the above ranges, a high degree of synergy is achieved between the various film layers, thereby contributing to a significant improvement in the passivation performance of the passivation silicon layers. For example, the thickness of the first passivation silicon layer 21 is 2.5 nm, 2.9 nm, 3.2 nm, 3.6 nm or 4 nm, etc.; the thickness of the second passivation silicon layer 22 is 0.5 nm, 0.7 nm, 0.9 nm, 1.2 nm or 1.5 nm, etc.; the thickness of the third passivation silicon layer 23 is 0.1 nm, 0.3 nm, 0.5 nm, 0.7 nm or 1 nm, etc.; and the thickness of the fourth passivation silicon layer 24 is 1.8 nm, 1.9 nm, 2.1 nm, 2.3 nm or 2.5 nm, etc.

[0057] This application discloses a photovoltaic module, which includes the heterojunction solar cell described above.

[0058] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0059] Example 1: This application provides a method for fabricating a heterojunction solar cell, which includes the following steps: Texturing of N-type silicon substrates.

[0060] A passivated silicon layer on the light-receiving surface of an N-type silicon substrate was prepared by PECVD. The process gases used included SiH4, N2O and H2, with a flow rate ratio of 1:(0~0.1):(0~25), a process gas pressure of 0.5 Torr~0.7 Torr, and an ignition power of 200 W~2500 W. The prepared passivated silicon layer consisted of a 1 nm thick anti-epitaxial layer, a 1.2 nm thick anti-yellowing powder layer, and a 4 nm thick main passivation layer, which were sequentially stacked on the light-receiving surface.

[0061] Fabrication of a backlight passivation silicon layer on the backlight side of an N-type silicon substrate: When the second passivated silicon layer was prepared by PECVD, the deposition gas source included a fourth silane, the flow rate of the fourth silane was 4500 sccm, the ignition power was 2500 W, and the pressure was 5 Torr, and a second passivated silicon layer with a thickness of 1 nm was obtained. When the third passivated silicon layer was prepared by PECVD, the deposition gas source included fifth silane, the flow rate of fifth silane was 4200 sccm, the ignition power was 2800 W, and the pressure was 0.4 Torr, and a third passivated silicon layer with a thickness of 0.8 nm was obtained. When the fourth passivated silicon layer was prepared by PECVD, the deposition gas source included sixth silane and third hydrogen, the flow ratio of sixth silane and third hydrogen was 1:1, the ignition power was 800 W, the pressure was 0.5 Torr, and a fourth passivated silicon layer with a thickness of 2 nm was obtained. When the first passivated silicon layer was prepared by PECVD, the deposition gas source included seventh silane and fourth hydrogen, the flow ratio of seventh silane and fourth hydrogen was 1:20, the ignition power was 16000 W, the pressure was 1.2 Torr, and a first passivated silicon layer with a thickness of 3 nm was obtained.

[0062] The first surface of the first passivated silicon layer on the backlight is doped using a PECVD method by introducing a doping gas source and an auxiliary gas source. The doping gas source includes carbon dioxide, and the auxiliary gas source includes a first silane. The flow ratio of the first silane to carbon dioxide is 1:100, the ignition time is 5 s, the ignition power is 2500 W, and the pressure is 1.2 Torr.

[0063] A backlight-doped silicon layer is deposited on the first surface using PECVD: A first doped silicon layer was prepared on the first surface at a pressure of 8 Torr. The deposition gas source included a second silane and a first hydrogen gas with a flow ratio of 1:100. The ignition power was 17000 W. The thickness of the first doped silicon layer was 1.8 nm. A second doped silicon layer was prepared on the first doped silicon layer. The deposition gas source included third silane, B2H6 and second hydrogen. The flow rate ratio of third silane, impurity source and second hydrogen was 1:2:300. The ignition power was 40000 W and the pressure was 4.9 Torr. The thickness of the second doped silicon layer was 25 nm. The crystallinity of the final doped silicon layer was 70% and the light transmittance was 85%.

[0064] A photosensitive doped silicon layer was prepared on a photosensitive passivated silicon layer using PECVD. The process gases were SiH4, N2O, PH3, and H2, with a process gas pressure of 4 Torr to 6 Torr and an ignition power of 6000 W to 12000 W. The gas flow rate ratio of SiH4, N2O, PH3, and H2 was 1:(0 to 8):(0 to 8):(180 to 350), and the ignition time was 100 s to 250 s. The resulting film thickness was 20 nm.

[0065] Post-processing steps include: Transparent conductive layers are fabricated on the silicon-doped layer on the light-receiving side and the silicon-doped layer on the backlight side, respectively. A heterojunction solar cell was fabricated by printing silver electrodes on a transparent conductive layer.

[0066] Example 2: The only difference between this embodiment and Embodiment 1 is that the flow rate ratio of the auxiliary gas source and the doping gas source is 1:50.

[0067] Example 3: The only difference between this embodiment and Embodiment 1 is that the flow rate ratio of the auxiliary gas source and the doping gas source is 1:200.

[0068] Example 4: The only difference between this embodiment and Embodiment 1 is that the flow rate ratio of the auxiliary gas source and the doping gas source is 1:40.

[0069] Example 5: The only difference between this embodiment and Embodiment 1 is that the flow rate ratio of the auxiliary gas source and the doping gas source is 1:210.

[0070] Example 6: The only difference between this embodiment and Embodiment 1 is that the pressure of the first doped silicon layer is 6 Torr.

[0071] Example 7: The only difference between this embodiment and Embodiment 1 is that the pressure of the first doped silicon layer is 9 Torr.

[0072] Example 8: The only difference between this embodiment and Embodiment 1 is that the pressure of the first doped silicon layer is 4 Torr.

[0073] Example 9: The only difference between this embodiment and Embodiment 1 is that the pressure of the first doped silicon layer is 11 Torr.

[0074] Example 10: The only difference between this embodiment and Embodiment 1 is that the auxiliary gas source is B2H6 and the doping gas source is methane.

[0075] Example 11: The only difference between this embodiment and Embodiment 1 is that the passivation silicon layer on the light-receiving side of the silicon substrate is also doped. That is, the passivation silicon layers on both the light-receiving and backlighting sides are doped, and the crystallization induction of the doped silicon layer is induced by the treated passivation silicon layer.

[0076] Comparative Example 1: The only difference between this comparative example and Example 1 is that the first surface is not doped; that is, the first doped silicon layer is directly prepared on the surface of the prepared first passivated silicon layer, and oxygen is introduced during the preparation of the first doped silicon layer to achieve the effect of crystallization induction.

[0077] Comparative Example 2: The only difference between this comparative example and Example 1 is that only carbon dioxide is used to dope the first surface of the first passivated silicon layer.

[0078] Comparative Example 3: The only difference between this comparative example and Example 1 is that only the first surface of the first passivated silicon layer is treated with the first silane.

[0079] Performance testing The solar cells prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to the following related tests: This application describes the performance testing of a heterojunction solar cell using a GIV-60 testing machine manufactured by Zhongsen Electric Technology Co., Ltd., focusing on open-circuit voltage, short-circuit current, and fill factor. The silicon wafer of the tested heterojunction solar cell measures 210.6 mm × 71 mm, with a calibrated light intensity of 1000 ± 5 W / m². The experimental results are shown in Table 1, which presents the performance test results of the heterojunction solar cell.

[0080] Table 1 Performance test results of heterojunction solar cells

[0081] Comparing the data of Example 1 with those of Comparative Examples 1 to 3, it can be seen that the photoelectric conversion efficiency of Example 1 is better than that of Comparative Examples 1 to 3. This demonstrates that by using a doping gas source and an auxiliary gas source to dope the first surface of the first passivated silicon layer, the doped first surface can serve as a crystallization induction source for the first doped silicon layer, enhancing its crystallinity and improving light transmittance; simultaneously, the auxiliary gas source can be used to optimize the interface between the first doped silicon layer and the first passivated silicon layer, thereby improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0082] Comparing the data from Examples 1 to 5, it can be seen that the photoelectric conversion efficiency of Examples 1 to 3 is better than that of Examples 4 and 5. This indicates that the flow rate ratio of the auxiliary gas source to the doped gas source in Examples 1 to 3 is more optimal. A better flow rate ratio helps to improve the synergistic effect of the two, thereby significantly improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0083] Comparing the data from Examples 1, 6 to 9, it can be seen that the photoelectric conversion efficiency of Examples 1, 6 to 7 is better than that of Examples 8 and 9. This indicates that the pressure on the first doped silicon layer in Examples 1, 6 to 7 is more suitable. A more suitable pressure helps to reduce the loss of the first passivation layer during the preparation of the first doped silicon layer, thereby further improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0084] Comparing the data from Example 1 and Example 10, it can be seen that the photoelectric conversion efficiency of Example 1 is better than that of Example 10. Therefore, using carbon dioxide as the doping gas source and the first silane as the auxiliary gas source is more conducive to further improving the light transmittance of the crystallinity of the first doped silicon layer and thus improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0085] Comparing the data from Example 1 and Example 11, it can be seen that the photoelectric conversion efficiency of Example 1 is better than that of Example 11. This demonstrates that doping the passivation silicon layer on both the light-receiving and back-light-receiving surfaces helps to improve the crystallinity of the doped silicon layer, thereby increasing the photoelectric conversion efficiency of the solar cell.

[0086] The heterojunction solar cell, its preparation method, and photovoltaic module disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the heterojunction solar cell, its preparation method, and photovoltaic module. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for fabricating a heterojunction solar cell, characterized in that, The preparation method includes the following steps: A substrate having a first passivated silicon layer is provided, the first passivated silicon layer including a first surface facing away from the substrate and a second surface facing the substrate; The first surface of the first passivated silicon layer is doped using a doping gas source and an auxiliary gas source. A first doped silicon layer is deposited on the first surface; Post-processing yields the heterojunction solar cell; The auxiliary gas source is a first silane and / or an impurity source used to form the first doped silicon layer, wherein the doped gas source contains carbon and / or oxygen elements.

2. The preparation method according to claim 1, characterized in that, The flow rate ratio of the auxiliary gas source to the doped gas source is 1:50 to 1:

200.

3. The preparation method according to claim 1, characterized in that, The first surface was subjected to the doping treatment using PECVD, with an ignition time of 4 s to 10 s, an ignition power of 2000 W to 3000 W, and a pressure of 1 Torr to 1.5 Torr.

4. The preparation method according to claim 1, characterized in that, The doping gas source includes at least one of carbon dioxide, nitrous oxide, and methane; and / or, When the auxiliary gas source includes the impurity source, the impurity source satisfies one of the following conditions: When the first doped silicon layer is a P-type doped layer, the impurity source in the auxiliary gas source includes at least one of BH3, TMB, BCl3, and B2H6. When the first doped silicon layer is an N-type doped layer, the impurity source in the auxiliary gas source includes PH3.

5. The preparation method according to claim 1, characterized in that, When the first doped silicon layer is prepared by PECVD, the pressure is 6 Torr to 9 Torr.

6. The preparation method according to claim 5, characterized in that, When preparing the first doped silicon layer, the deposition gas source includes a second silane and a first hydrogen gas, the flow ratio of the second silane and the first hydrogen gas is 1:50 to 1:200, and the ignition power is 15000 W to 20000 W.

7. The preparation method according to claim 1, characterized in that, After the step of depositing a first doped silicon layer on the first surface and before the post-processing step, the fabrication method further includes: fabricating a second doped silicon layer on the first doped silicon layer; When the second doped silicon layer is prepared by PECVD, the deposition gas source includes a third silane, the impurity source and a second hydrogen gas. The flow rate ratio of the third silane, the impurity source and the second hydrogen gas is 1:(0.2~2.5):(200~400), the ignition power is 30000 W~50000 W, and the pressure is 4.5 Torr~5.8 Torr.

8. The preparation method according to claim 1, characterized in that, Before the step of using an auxiliary gas source and a doping gas source to dope the first surface of the first passivated silicon layer, the preparation method further includes: sequentially preparing a second passivated silicon layer, a third passivated silicon layer, a fourth passivated silicon layer, and the first passivated silicon layer on a substrate. In the process of preparing the second passivated silicon layer using PECVD, the deposition gas source includes a fourth silane, wherein the flow rate of the fourth silane is 3000 sccm~5000 sccm, the ignition power is 2000 W~3000 W, and the pressure is 0.5 Torr~10.8 Torr; and / or, When preparing the third passivated silicon layer using PECVD, the deposition gas source includes a fifth silane, wherein the flow rate of the fifth silane is 3000 sccm~5000 sccm, the ignition power is 2000 W~3000 W, and the pressure is 0.3 Torr~0.5 Torr; and / or, When the fourth passivated silicon layer is prepared using PECVD, the deposition gas source includes a sixth silane and a third hydrogen gas, with a flow rate ratio of 1:0.5 to 1:2, an ignition power of 500 W to 1000 W, and a pressure of 0.3 Torr to 0.6 Torr; and / or, When the first passivated silicon layer is prepared by PECVD, the deposition gas source includes seventh silane and fourth hydrogen, the flow ratio of the seventh silane and the fourth hydrogen is 1:10 to 1:30, the ignition power is 10000 W to 20000 W, and the pressure is 1 Torr to 1.5 Torr.

9. A heterojunction solar cell, characterized in that, The heterojunction solar cell includes the heterojunction solar cell prepared by the preparation method according to any one of claims 1 to 8.

10. The heterojunction solar cell according to claim 9, characterized in that, The heterojunction solar cell includes a substrate, and a passivated silicon layer, a doped silicon layer, a transparent conductive layer, and an electrode sequentially stacked on the substrate. The passivation silicon layer includes a second passivation silicon layer, a third passivation silicon layer, a fourth passivation silicon layer, and a first passivation silicon layer stacked on the substrate; the doped silicon layer includes a first doped silicon layer and a second doped silicon layer stacked sequentially on the first passivation silicon layer.

11. The heterojunction solar cell according to claim 10, characterized in that, The crystallinity of the doped silicon layer is 60%~80%; and / or, The light transmittance of the doped silicon layer is 70%~95%; and / or, The thickness of the second doped silicon layer is 20 nm to 30 nm; and / or, The thickness of the first doped silicon layer is 1.5 nm to 2 nm; and / or, The thickness of the first passivated silicon layer is 2.5 nm to 4 nm; and / or, The thickness of the second passivated silicon layer is 0.5 nm to 1.5 nm; and / or, The thickness of the third passivation silicon layer is 0.1 nm to 1 nm; and / or, The thickness of the fourth passivation silicon layer is 1.8 nm to 2.5 nm.

12. A photovoltaic module, characterized in that, The photovoltaic module includes: a heterojunction solar cell as described in any one of claims 9 to 11.

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